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gstreamer/gst/gstmeta.h
Tim-Philipp Müller f62ee97592 buffer: store sequence number for metas 
For metas where order might be significant if multiple metas are
attached to the same buffer, so store a sequence number with the
meta when adding it to the buffer. This allows users of the meta
to make sure metas are processed in the right order.

We need a 64-bit integer for the sequence number here in the API,
a 32-bit one might overflow too easily with high packet/buffer
rates. We could do it rtp-seqnum style of course, but that's a
bit of a pain.

We could also make it so that gst_buffer_add_meta() just keeps metas in
order or rely on the order we add the metas in, but that seems too
fragile overall, when buffers (incl. metas) get merged or split.

Also add a compare function for easier sorting.

We store the seqnum in the MetaItem struct here and not in the
GstMeta struct since there's no padding in the GstMeta struct.
We could add a private struct to GstMeta before the start of
GstMeta, but that's what MetaItem effectively is implementation-
wise. We can still change this later if we want, since it's all
private.

Fixes #262
2019-02-12 17:53:08 +00:00

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/* GStreamer
* Copyright (C) 2009 Wim Taymans <wim.taymans@gmail.be>
*
* gstmeta.h: Header for Metadata structures
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
#ifndef __GST_META_H__
#define __GST_META_H__
#include <glib.h>
G_BEGIN_DECLS
typedef struct _GstMeta GstMeta;
typedef struct _GstMetaInfo GstMetaInfo;
#define GST_META_CAST(meta) ((GstMeta *)(meta))
/**
* GstMetaFlags:
* @GST_META_FLAG_NONE: no flags
* @GST_META_FLAG_READONLY: metadata should not be modified
* @GST_META_FLAG_POOLED: metadata is managed by a bufferpool
* @GST_META_FLAG_LOCKED: metadata should not be removed
* @GST_META_FLAG_LAST: additional flags can be added starting from this flag.
*
* Extra metadata flags.
*/
typedef enum {
GST_META_FLAG_NONE = 0,
GST_META_FLAG_READONLY = (1 << 0),
GST_META_FLAG_POOLED = (1 << 1),
GST_META_FLAG_LOCKED = (1 << 2),
GST_META_FLAG_LAST = (1 << 16)
} GstMetaFlags;
/**
* GST_META_FLAGS:
* @meta: a #GstMeta.
*
* A flags word containing #GstMetaFlags flags set on @meta
*/
#define GST_META_FLAGS(meta) (GST_META_CAST (meta)->flags)
/**
* GST_META_FLAG_IS_SET:
* @meta: a #GstMeta.
* @flag: the #GstMetaFlags to check.
*
* Gives the status of a specific flag on a metadata.
*/
#define GST_META_FLAG_IS_SET(meta,flag) !!(GST_META_FLAGS (meta) & (flag))
/**
* GST_META_FLAG_SET:
* @meta: a #GstMeta.
* @flag: the #GstMetaFlags to set.
*
* Sets a metadata flag on a metadata.
*/
#define GST_META_FLAG_SET(meta,flag) (GST_META_FLAGS (meta) |= (flag))
/**
* GST_META_FLAG_UNSET:
* @meta: a #GstMeta.
* @flag: the #GstMetaFlags to clear.
*
* Clears a metadata flag.
*/
#define GST_META_FLAG_UNSET(meta,flag) (GST_META_FLAGS (meta) &= ~(flag))
/**
* GST_META_TAG_MEMORY_STR:
*
* This metadata stays relevant as long as memory layout is unchanged.
*
* Since: 1.2
*/
#define GST_META_TAG_MEMORY_STR "memory"
/**
* GstMeta:
* @flags: extra flags for the metadata
* @info: pointer to the #GstMetaInfo
*
* Base structure for metadata. Custom metadata will put this structure
* as the first member of their structure.
*/
struct _GstMeta {
GstMetaFlags flags;
const GstMetaInfo *info;
};
#include <gst/gstbuffer.h>
/**
* GstMetaInitFunction:
* @meta: a #GstMeta
* @params: parameters passed to the init function
* @buffer: a #GstBuffer
*
* Function called when @meta is initialized in @buffer.
*/
typedef gboolean (*GstMetaInitFunction) (GstMeta *meta, gpointer params, GstBuffer *buffer);
/**
* GstMetaFreeFunction:
* @meta: a #GstMeta
* @buffer: a #GstBuffer
*
* Function called when @meta is freed in @buffer.
*/
typedef void (*GstMetaFreeFunction) (GstMeta *meta, GstBuffer *buffer);
/**
* gst_meta_transform_copy:
*
* GQuark for the "gst-copy" transform.
*/
GST_API GQuark _gst_meta_transform_copy;
/**
* GST_META_TRANSFORM_IS_COPY:
* @type: a transform type
*
* Check if the transform type is a copy transform
*/
#define GST_META_TRANSFORM_IS_COPY(type) ((type) == _gst_meta_transform_copy)
/**
* GstMetaTransformCopy:
* @region: %TRUE if only region is copied
* @offset: the offset to copy, 0 if @region is %FALSE, otherwise > 0
* @size: the size to copy, -1 or the buffer size when @region is %FALSE
*
* Extra data passed to a "gst-copy" transform #GstMetaTransformFunction.
*/
typedef struct {
gboolean region;
gsize offset;
gsize size;
} GstMetaTransformCopy;
/**
* GstMetaTransformFunction:
* @transbuf: a #GstBuffer
* @meta: a #GstMeta
* @buffer: a #GstBuffer
* @type: the transform type
* @data: transform specific data.
*
* Function called for each @meta in @buffer as a result of performing a
* transformation on @transbuf. Additional @type specific transform data
* is passed to the function as @data.
*
* Implementations should check the @type of the transform and parse
* additional type specific fields in @data that should be used to update
* the metadata on @transbuf.
*
* Returns: %TRUE if the transform could be performed
*/
typedef gboolean (*GstMetaTransformFunction) (GstBuffer *transbuf,
GstMeta *meta, GstBuffer *buffer,
GQuark type, gpointer data);
/**
* GstMetaInfo:
* @api: tag identifying the metadata structure and api
* @type: type identifying the implementor of the api
* @size: size of the metadata
* @init_func: function for initializing the metadata
* @free_func: function for freeing the metadata
* @transform_func: function for transforming the metadata
*
* The #GstMetaInfo provides information about a specific metadata
* structure.
*/
struct _GstMetaInfo {
GType api;
GType type;
gsize size;
GstMetaInitFunction init_func;
GstMetaFreeFunction free_func;
GstMetaTransformFunction transform_func;
/* No padding needed, GstMetaInfo is always allocated by GStreamer and is
* not subclassable or stack-allocatable, so we can extend it as we please
* just like interfaces */
};
GST_API
GType gst_meta_api_type_register (const gchar *api,
const gchar **tags);
GST_API
gboolean gst_meta_api_type_has_tag (GType api, GQuark tag);
GST_API
const GstMetaInfo * gst_meta_register (GType api, const gchar *impl,
gsize size,
GstMetaInitFunction init_func,
GstMetaFreeFunction free_func,
GstMetaTransformFunction transform_func);
GST_API
const GstMetaInfo * gst_meta_get_info (const gchar * impl);
GST_API
const gchar* const* gst_meta_api_type_get_tags (GType api);
GST_API
guint64 gst_meta_get_seqnum (const GstMeta * meta);
GST_API
gint gst_meta_compare_seqnum (const GstMeta * meta1,
const GstMeta * meta2);
/* some default tags */
GST_API GQuark _gst_meta_tag_memory;
/**
* GST_META_TAG_MEMORY:
*
* Metadata tagged with this tag depends on the particular memory
* or buffer that it is on.
*
* Deprecated: The GQuarks are not exported by any public API, use
* GST_META_TAG_MEMORY_STR instead.
*/
#ifndef GST_DISABLE_DEPRECATED
#define GST_META_TAG_MEMORY (_gst_meta_tag_memory)
#endif
G_END_DECLS
#endif /* __GST_META_H__ */
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